Chapter 15 Flashcards
1
Q
what is corrosion caused by?
A
chemical reactions between the metal and the chemicals in the environment
2
Q
what is rusting?
A
the corrosion of iron
3
Q
what two conditions are needed for iron to rust?
A
oxygen and water
4
Q
why does the mass of iron increase as it rusts?
A
the atoms bond with the oxygen and water molecules, which makes a compound that is heavier than iron
5
Q
equation for the rusting of iron III
A
iron + oxygen + water -> hydrated iron (III) oxide
6
Q
what happens to the iron when it rusts?
A
it is oxidised
7
Q
3 ways of barriers to stop rusting
A
paint
oil/grease
plastic
8
Q
what is the sacrificial method of preventing rusting?
A
a more reactive metal is placed onto the iron so the iron stays intact
9
Q
what happens when iron is galvanised?
A
it is covered with a layer of zinc so the oxygen and water oxidise and react with zinc, not iron
10
Q
why isn’t aluminium completely destroyed by corrosion?
A
aluminium oxide forms a protective layer that stops any further reactions taking place
11
Q
why is iron completely destroyed by rusting?
A
iron oxide is flaky and will fall off to leave more iron exposed to react again
12
Q
what is an alloy?
A
a mixture of a metal and another material
13
Q
why are alloys much harder than normal metals?
A
the structure of the metal is disrupted so the layers can’t slide over eachother
14
Q
what is bronze made from?
A
copper + tin
15
Q
why is bronze better than copper?
A
it is much harder
16
Q
uses of bronze 3
A
make medals, decorative ornaments and statues
17
Q
what is brass made from?
A
copper + zinc
18
Q
why is brass better than bronze?
A
it is more malleable and is used where there needs to be little friction
19
Q
uses of brass 3
A
musical instruments, taps, door fittings
20
Q
what is the most useful property of aluminium?
A
its low density
21
Q
why is aluminium alloyed?
A
to make it stronger
22
Q
uses of aluminium alloys 2
A
aircraft
plating on military vehicles
23
Q
why is gold alloyed?
A
to make it stronger
24
Q
why is copper mixed with gold?
A
it is more long wearing
25
uses of gold alloys
jewellery
26
what is 24 carat gold?
pure gold
27
how to work out how much gold is in a carat?
divide number by 24
28
what are steels?
alloys of iron with carbon and other elements
29
what are the simplest steels?
carbon steels
30
how are carbon steels made?
most of the carbon is removed is removed from the iron
31
uses of carbon steels 3
car bodies
ships
structural steel
32
properties of high carbon steels 2
strong but brittle
33
properties of low carbon steels 2
soft and easily shaped
34
what are nickel-steel alloys used for and why?
long-span bridges, bicycle chains
| resistant to stretching forces
35
what is stainless steel made from?
chromium and nickel
36
characteristics of stainless steel? 2
don't rust
| very strong
37
uses of stainless steels
cutlery, cooking utensils,
38
what do the properties of a polymer depend on?
the monomers used to make it
| the conditions under which the reaction happened
39
what are the two types of polyethene?
low density polyethene
| high density polyethene
40
how is low density polyethene made?
very high temperatures and a catalyst
41
what is LD polyethene used for and why?
plastic bags and bottles
| it is very flexible
42
what gives LD polyethene its low density?
the polymer chains are randomly branched and can't pack closely together
43
how is HD polyethene made?
lower temperature (50c) and a different catalyst(
44
use of LD polyethene and why
water tanks
| it is very rigid
45
what gives HD polyethene its high density?
the polyethene chains are straighter and can pack together more closely
46
what are thermosetting polymers?
they don't soften when heated because of the 'cross links' between polymer chains
47
what are thermosoftening polymers?
they soften when heated
| made of individual polymer chains tangled together
48
what allows thermosoftening polymers to soften under heat?
weak intermolecular forces between the polymer chains that need little energy to overcome
when it cools, the forces bring the polymer back together again
49
what stops thermosetting polymers from softening under heat?
the monomers form covalent 'cross links' between polymer chains which are strong and won't soften
50
what is glass mainly made from?
sand
51
how is glass made?
the raw materials (sand, limestone and sodium carbonate) are heated to 1500c
they melt and react to form molten glass
when they cool, they remain in this disorganised structure
52
how to make different types of glass
use different raw materials
53
what is different about borosilicate glass and what is it used for?
it has boron trioxide in it
| it is used for oven ware as it has a high melting point
54
what are ceramics?
non metal solids with high melting points that aren't made from carbon based compounds
55
examples of ceramics made form clay 3
bricks, crockery and toilets
56
how are clay ceramics made?
wet clay is moulded into desired shape and heated at 1000c
57
why do the properties of clay change so drastically when heated?
there is ionic bonding between metals and non metals in clay
covalent bonding between non metals
arranged in giant layers
when wet, water gets between layers and makes them slimy
when they are heated, water is driven out and strong bonds form between layers
58
what are composites made from?
one material embedded in another
59
4 examples of composites
fibreglass
carbon fibre
concrete
wood
60
why is natural wood so strong?
cellulose
61
what is a matrix in a composite?
it acts as a binder and holds everything together
62
what is fibreglass made from?
fibres of glass embedded in a matrix made of plastic
63
properties of fibreglass 2
low density
| very strong
64
what is fibreglass used for? 3
skis
boats
surfboards
65
what is concrete made from?
aggregate (sand and gravel) embedded in cement
66
use of concrete
building materials
67
what is carbon fibre made from?
long chains of carbon atoms in plastic
| carbon nanotubes in plastic
68
use of carbon fibres
aerospace
| sports car manufacturing
69
what do most fertilisers contain?
nitrogen, phosphorous and potassium
70
why do fertilisers contain nitrogen and similar nutrients
crops grow and absorb nutrients for growth
farmers harvest plants, so little of the plant is allowed to decompose and add nutrients back to the soil
so farmers have to replace the missing nutrients or provide more of them
71
even though there is a lot of nitrogen in the air, why don't plants absorb it?
the gas is insoluble in water and plants can only absorb a soluble form of nitrogen
72
what is the haber process?
nitrogen and hydrogen are converted to ammonia, which is used in fertilisers
73
who created the haber process?
german scientist Fritz haber
74
what is the most important use of ammonia?
fertilisers
75
how is the nitrogen for the Haber process sourced?
obtained from the air
76
how is hydrogen sourced for the Haber process?
methane is reacted with steam to form hydrogen and carbon dioxide
77
what are the three conditions used in the haber process?
```
iron catalyst
high pressure (200 atmospheres)
high temperature (450c)
```
78
the Haber process:
nitrogen and methane are sourced
they are passed over an iron catalyst at high temperature and pressure
this reaction is reversible so some ammonia formed is converted back to the raw materials
a dynamic equilibrium is reached
ammonia formed as a gas
it is collected, condensed and turned into fertiliser
the unused reactants are recycled so nothing is wasted
79
how is ammonia obtained from the Haber process?
the gases are cooled
| ammonia liquefies and can be separated
80
equation for haber process
nitrogen + hydrogen (half arrows) ammonia (+ heat)
| N2 + 3H2 (half arrows) 2NH2 (+ heat)
81
equation for the formation of hydrogen
methane + steam -> hydrogen + carbon dioxide
82
why are fertilisers used?
replace missing nutrients
increases crop yield
crops grow faster and bigger
83
how to create ammonia nitrate
ammonia + nitric acid
84
how is ammonia phosphate formed?
ammonia + phosphoric acid
85
when are salts formed?
when acids and alkalis react together in a neutralisation reaction
86
is ammonia solution alkali or acid
alkali
87
how is ammonium nitrate formed in industry?
in giant vats
high concentrations
very exothermic reaction
the heat released evaporates water, leaving a very concentrated ammonium nitrate product
88
how is ammonium nitrate formed in the lab?
```
smaller scale
titration and crystallisation
reactants are at a lower concentration
less heat produced
after titration, the solution is crystallised to result in pure ammonium nitrate crystals
```
89
why is crystllisation not used in industry?
it is too slow
90
how to make ammonium sulfate?
react ammonia with sulfuric acid
91
what is NPK fertiliser?
Nitrogen, phosphorous and potassium fertiliser
92
where to source phosphorous?
rocks
93
why is acid added to phosphorous rocks?
plants can't use it as it is insoluble in water
94
what is produced when phosphate rock is reacted with nitric acid?
phosphoric acid and calcium nitrate
95
what is produced when phosphate rock is reacted with sulfuric acid?
calcium sulfate and calcuim phosphate
| also known as single superphosphate
96
what is produced when phosphate rock is reacted with phosphoric acid?
tripe superphosphate
97
how is nitrogen obtained from air?
air is cooled to -200c to liquefy it
| fractional distillation happens
98
reaction for methane + steam
methane + steam -> hydrogen + carbon monoxide
99
what is the main cost of producing ammonia?
sourcing the methane, which is a natural gas
100
why is 200 atmospheres of pressure used?
there are less moles of ammonia than reactants
so, higher pressure = higher yield
but, higher pressure is also expensive and dangerous
so 200 atmospheres is a compromise
101
why is an iron catalyst used?
it speeds up both the forward and reverse reaction
| doesn't affect yield of ammonia but makes it be produced quicker
102
what is the forward reaction of the production of ammonia?
exothermic
103
why is 450c used for the Haber process?
forward reaction is exothermic
increasing temperature = less yield
but decreasing temperature = slower rate of reaction and minimises effect of catalyst
450c is a compromise between maximum yield and speed of reaction
